No crash in this case, but I made the mistake of toggling to fullscreen mode on my netbook running Ubuntu 12.04. It's now impossible to escape this "No Menus" view, and it seems to have disabled the popout unity launcher as well. Steps I've already taken:

Alt-Tab to move to a different program, then back - QGIS remains in fullscreen

I am experiencing exactly the same problem with Ubuntu 12.04 and QGIS 1.8 It happened just after I clicked the fullscreen icon (the little square in the windows navigation pane) and I am unable to get QGIS started normally again. Rather it flickers horribly and cannot respond normally to mouse clicks. Ctrl-F does not fix the problem Rebooting does not fix the problem Will try to replace Ubuntu with Linux Mint 13 and let you know.
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user10675Oct 3 '12 at 2:44

4 Answers
4

I'm now convinced this is a unity/desktop switcher bug. The QGIS window appears in one desktop but the menu header appears in a separate desktop. I'm closing this as a lost cause, with apologies to anyone who spent time on this as a QGIS issue.

If you go into full screen mode then hover the cursor over the top middle of QGIS and wait a few milliseconds the full menu should appear then you can go to View>Toggle Full Screen Mode, (ctrl+f) seems to work to on my version.

I had the same problem. Recovered with Alt and right click on the top left corner, and send qgis to another work area. So you can see the hidden menu, and work normally.
last, you need to re-assign the "toggle fullscreen mode" because is assigned to another function. (press f2, config shortcuts)